Often complex electronic systems require the measurement of unsafe voltages. These voltages are typically those above 12-15 volts. Prior solutions have attempted to protect equipment and personnel from inadvertent encounters with unsafe voltages. Such encounters can result in electrical shock hazards to personnel, or damage or destruction of electrical circuits or surrounding equipment.
A typical solution reduces unsafe voltage with a voltage divider or resistor network. Such a circuit is shown in FIG. 1. Here an unsafe voltage input 12 is applied to conditioning circuit 10. For illustration purposes, resistor 14 and resistor 16 divide or reduce the unsafe input voltage and provide a reduced output voltage 18 as described by Equation 1:                     Vout        =                  Vin          ⁢                                           ⁢                                    R              16                                      (                                                R                  14                                +                                  R                  16                                            )                                                                    (                      Eq            .                                                   ⁢            1                    )                ⁢                                       Equation 1 shows the ratio by which the unsafe voltage is reduced. Here the unsafe voltage is reduced by the ratio of resistor 16 to the sum of resistor 16 and resistor 14. When resistor 14 has a much bigger value than resistor 16, output voltage 18 is significantly less than the unsafe input voltage 12. However, this simply solution has serious drawbacks. If resister 14 fails in a short circuit condition, output voltage 18 fails to equal voltage of unsafe input voltage 12. This situation can result in high voltages being unexpectedly applied to circuits and creating a shock hazard to personnel. Similarly, when resister 16 fails open, the output voltage 18 is again equal to the unsafe input voltage 12. Thus, one needs to condition the sampled input voltages with a circuit to provide safe conditioned voltages for measurement purposes. Additionally, these lower voltages are more safely routed through wires or other circuit paths to test the equipment 20. Any damage to these insulators containing voltages 18 may pose a shock hazard to personnel or surrounding equipment if this voltage is at an unsafe level.